Add ChannelSigner::get_holder_anchor_input_witness_weight

Author: tankyleo

lightning/src/events/bump_transaction.rs

@@ -20,7 +20,7 @@ use crate::io_extras::sink;
 use crate::ln::channel::ANCHOR_OUTPUT_VALUE_SATOSHI;
 use crate::ln::types::ChannelId;
 use crate::ln::chan_utils;
-use crate::ln::chan_utils::{ANCHOR_INPUT_WITNESS_WEIGHT, HTLCOutputInCommitment};
+use crate::ln::chan_utils::HTLCOutputInCommitment;
 use crate::prelude::*;
 use crate::sign::{
 	ChannelDerivationParameters, ChannelSigner, HTLCDescriptor, SignerProvider, P2WPKH_WITNESS_WEIGHT,
@@ -608,14 +608,17 @@ where
 		&self, claim_id: ClaimId, package_target_feerate_sat_per_1000_weight: u32,
 		commitment_tx: &Transaction, commitment_tx_fee_sat: u64, anchor_descriptor: &AnchorDescriptor,
 	) -> Result<(), ()> {
+		let signer = anchor_descriptor.derive_channel_signer(&self.signer_provider);
+		let anchor_input_witness_weight = signer.get_holder_anchor_input_witness_weight();
+
 		// Our commitment transaction already has fees allocated to it, so we should take them into
 		// account. We do so by pretending the commitment transaction's fee and weight are part of
 		// the anchor input.
 		let mut anchor_utxo = anchor_descriptor.previous_utxo();
 		let commitment_tx_fee_sat = Amount::from_sat(commitment_tx_fee_sat);
 		anchor_utxo.value += commitment_tx_fee_sat;
 		let starting_package_and_fixed_input_satisfaction_weight =
-			commitment_tx.weight().to_wu() + ANCHOR_INPUT_WITNESS_WEIGHT + EMPTY_SCRIPT_SIG_WEIGHT;
+			commitment_tx.weight().to_wu() + anchor_input_witness_weight + EMPTY_SCRIPT_SIG_WEIGHT;
 		let mut package_and_fixed_input_satisfaction_weight =
 			starting_package_and_fixed_input_satisfaction_weight;
 
@@ -640,7 +643,7 @@ where
 				output: vec![],
 			};
 
-			let total_satisfaction_weight = ANCHOR_INPUT_WITNESS_WEIGHT + EMPTY_SCRIPT_SIG_WEIGHT +
+			let total_satisfaction_weight = anchor_input_witness_weight + EMPTY_SCRIPT_SIG_WEIGHT +
 				coin_selection.confirmed_utxos.iter().map(|utxo| utxo.satisfaction_weight).sum::<u64>();
 			let total_input_amount = must_spend_amount +
 				coin_selection.confirmed_utxos.iter().map(|utxo| utxo.output.value).sum();
@@ -686,7 +689,6 @@ where
 			log_debug!(self.logger, "Signing anchor transaction {}", anchor_txid);
 			anchor_tx = self.utxo_source.sign_psbt(anchor_psbt)?;
 
-			let signer = anchor_descriptor.derive_channel_signer(&self.signer_provider);
 			anchor_tx = signer.spend_holder_anchor_input(&anchor_tx, 0, &self.secp)?;
 
 			#[cfg(debug_assertions)] {
@@ -857,7 +859,7 @@ mod tests {
 	use super::*;
 
 	use crate::io::Cursor;
-	use crate::ln::chan_utils::ChannelTransactionParameters;
+	use crate::ln::chan_utils::{ANCHOR_INPUT_WITNESS_WEIGHT, ChannelTransactionParameters};
 	use crate::util::ser::Readable;
 	use crate::util::test_utils::{TestBroadcaster, TestLogger};
 	use crate::sign::KeysManager;

lightning/src/sign/mod.rs

@@ -45,6 +45,7 @@ use crate::ln::chan_utils::{
 	get_anchor_redeemscript, get_counterparty_payment_script, get_revokeable_redeemscript,
 	make_funding_redeemscript, ChannelPublicKeys, ChannelTransactionParameters, ClosingTransaction,
 	CommitmentTransaction, HTLCOutputInCommitment, HolderCommitmentTransaction,
+	ANCHOR_INPUT_WITNESS_WEIGHT,
 };
 use crate::ln::channel::ANCHOR_OUTPUT_VALUE_SATOSHI;
 use crate::ln::channel_keys::{
@@ -969,6 +970,9 @@ pub trait ChannelSigner {
 	fn spend_holder_anchor_input(
 		&self, anchor_tx: &Transaction, input_idx: usize, secp_ctx: &Secp256k1<secp256k1::All>,
 	) -> Result<Transaction, ()>;
+
+	/// Get the weight of the witness to spend the holder anchor input
+	fn get_holder_anchor_input_witness_weight(&self) -> u64;
 }
 
 /// Specifies the recipient of an invoice.
@@ -1908,6 +1912,10 @@ impl ChannelSigner for InMemorySigner {
 		tx.input[input_idx].witness = witness;
 		Ok(tx)
 	}
+
+	fn get_holder_anchor_input_witness_weight(&self) -> u64 {
+		ANCHOR_INPUT_WITNESS_WEIGHT
+	}
 }
 
 const MISSING_PARAMS_ERR: &'static str =

lightning/src/util/test_channel_signer.rs

@@ -8,7 +8,7 @@
 // licenses.
 
 use crate::ln::channel::{ANCHOR_OUTPUT_VALUE_SATOSHI, MIN_CHAN_DUST_LIMIT_SATOSHIS};
-use crate::ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, HolderCommitmentTransaction, CommitmentTransaction, ChannelTransactionParameters, TrustedCommitmentTransaction, ClosingTransaction};
+use crate::ln::chan_utils::{ANCHOR_INPUT_WITNESS_WEIGHT, HTLCOutputInCommitment, ChannelPublicKeys, HolderCommitmentTransaction, CommitmentTransaction, ChannelTransactionParameters, TrustedCommitmentTransaction, ClosingTransaction};
 use crate::ln::channel_keys::{HtlcKey};
 use crate::ln::msgs;
 use crate::types::payment::PaymentPreimage;
@@ -371,6 +371,10 @@ impl ChannelSigner for TestChannelSigner {
 	) -> Result<Transaction, ()> {
 		self.inner.spend_holder_anchor_input(anchor_tx, input_idx, secp_ctx)
 	}
+
+	fn get_holder_anchor_input_witness_weight(&self) -> u64 {
+		ANCHOR_INPUT_WITNESS_WEIGHT
+	}
 }
 
 impl EcdsaChannelSigner for TestChannelSigner {